Constant temperature type crystal oscillator

ABSTRACT

A lead wire led-out type crystal oscillator of constant temperature type for high stability is disclosed, which includes a heat supply body that supplies heat to a crystal resonator from which a plurality of lead wires are led out, to maintain the temperature constant. The heat supply body includes a heat conducting plate which has through-holes for the lead wires and is mounted on the circuit board, and which faces, and is directly thermally joined to, the crystal resonator and a chip resistor for heating which is mounted on the circuit board adjacent to the heat conducting plate, and is thermally joined to the heat conducting plate.

BACKGROUND OF THE INVENTION

The present invention relates to a highly stable crystal oscillator oflead wire led-out type and constant temperature type (hereunder referredto as highly stable oscillator), and particularly relates to a highlystable oscillator which is effective in heat utilization

The frequency stability of this kind of highly stable oscillator ishigh, since the operating temperature of a crystal resonator ismaintained constant by a thermostat. Therefore, a highly stableoscillator of this kind is used industrially in optical communicationbase stations for example. Recently, miniaturization has spread even tothese highly stable oscillators, and corresponding miniaturization hasbeen required.

FIG. 2A and FIG. 2B are diagrams describing one conventional example ofa lead wire led-out type crystal oscillator of this kind. FIG. 2A is avertical sectional view of the highly stable oscillator, and FIG. 2B isa perspective view of the lead wire led-out type crystal resonator usedtherefor.

As shown in FIG. 2A, the highly stable oscillator of this kind comprisesa first circuit board 1 a and a second circuit board 1 b. The firstcircuit board 1 a is supported by metallic pins 3 a serving as externalterminals which are insulated from and pass through a metallic base 2. Athermostat 4 and temperature control elements 5 are arranged so as toconstruct a temperature control mechanism that maintains the temperatureof the thermostat 4 constant. The thermostat 4 comprises a metalliccylinder having one open end. A heating coil 6 is wound around theperiphery thereof, and a thermistor 5 a is fitted as a temperaturedetection element. Moreover, the thermostat 4 is secured on a powertransistor 5 b used for electricity control, which is disposed on thefirst circuit board 1 a.

The second circuit board 1 b is supported by metallic pins 3 b placed onthe first circuit board 1 a, and blocks off an upper opening face of thethermostat 4. Moreover a crystal resonator 7 and oscillating elements 8are disposed on both opposite principal planes of the second circuitboard 1 b, thereby constructing an oscillating circuit. This oscillatingcircuit is a voltage control type, having a voltage-variable capacitiveelement 8 a for example.

As shown in FIG. 2B, the crystal resonator 7 of this kind of crystaloscillator comprises for example an AT cut or SC cut crystal piece 7 bsealed off inside a metallic container 7 a (TO5 type) with five leadwires 9 leading out from its bottom. This crystal piece 7 b is retainedinside the metallic container 7 a while maintaining its plate facehorizontal, and is employed as a highly stable oscillator, particularlyfor communication equipment.

The lead wires 9 of the crystal resonator 7 pass through the secondcircuit board 1 b and are secured thereon by soldering, and the metalliccontainer 7 a of the crystal resonator 7 disposed on the one principalplane is accommodated in the thermostat 4. Furthermore, the highlytemperature-dependent oscillating elements 8, the characteristics ofwhich fluctuate according to the temperature of voltage-variablecapacitive elements 8 a and the like, are disposed on the otherprincipal plane of the second circuit board 1 b, and are accommodated inthe thermostat 4. Then they are covered with a metallic cover 10.

According to such a conventional highly stable oscillator, the operatingtemperature of the crystal resonator 7 is kept constant by thethermostat 4, so that frequency fluctuations in the oscillationfrequency due to temperature variations can be prevented. In otherwords, fluctuations in the oscillating frequency based on the frequencytemperature characteristics of the crystal resonator 7 can be prevented.Moreover, since the second circuit board 1 b mounted with theoscillating elements 8 is disposed on the thermostat 4, frequencyfluctuations due to the temperature characteristics of the circuitelements themselves are also prevented. Since highlytemperature-dependent, highly heat sensitive elements such as inparticular the voltage-variable capacitive elements 8 a are accommodatedinside the thermostat 4, the highly stable oscillator can furtherincrease the frequency stability, for example can maintain a frequencydeviation of 0.05 ppm or less. Therefore, the highly stable oscillatoris employed particularly for industrial purposes.

Moreover, with the conventional highly stable oscillator, thetemperature control mechanism including the thermostat 4 is disposed onthe first circuit board 1 a, and an oscillating circuit including thecrystal resonator 7 is disposed on the second circuit board 1 b.Therefore, the temperature control mechanism and the oscillating circuitcan be manufactured separately, and hence their design and manufacturecan be facilitated. Furthermore, the oscillating elements 8 are mountedon the second circuit board 1 b, and are electrically connected to thefirst circuit board 1 a by the metallic pins 3 b. Here, the firstcircuit board 1 a is not directly led out externally, and hence heatdissipation to the outside can be prevented (see Japanese UnexaminedPatent Publication KOKAI No, Hei 01-195706).

However, since the temperature control mechanism and the oscillatingcircuit are separately manufactured for the conventional highly stableoscillator of the above construction, the first circuit board 1 a andthe second circuit board 1 b are necessary. Furthermore, since thethermostat 4 that accommodates the crystal resonator 7 is used, anincrease in the size of the oscillator cannot be avoided. In particular,since the first circuit board 1 a and the second circuit board 1 b arearranged so that they are vertically opposed to each other, there hasbeen a problem of an increase the height dimension of the oscillatoritself.

Moreover, the oscillator also has had a problem in that the oscillatoritself becomes expensive since the thermostat 4 with the heating coil 6wound therearound is used separately from the crystal resonator 7. Thereis an oscillator that uses the metallic container 7 a of the crystalresonator 7 also for the thermostat 4. However, in either case, therehas been a problem in that the manufacturing operation becomestroublesome, and the oscillator itself becomes more expensive because ofa need for winding the heating coil 6 around the thermostat 4.

An object of the present invention is to provide a highly stableoscillator, the structure of which is simpler, and in particular, whichis of reduced height dimensions.

Moreover, the present invention relates to a constant temperature typecrystal oscillator that uses a surface mounted crystal resonator (SMD:abbreviation of Surface Mounted Device), and particularly relates to aconstant temperature type crystal oscillator having a simple structure.

FIG. 6 is a diagram for explaining one example of a conventional surfacemounted crystal oscillator of this kind, wherein FIG. 6A is a verticalsectional view of a constant temperature type crystal oscillator, andFIG. 6B is a schematic diagram showing a crystal oscillator insertedinto a thermostat.

A crystal oscillator of this kind comprises; a crystal resonator 22, athermostat 23, oscillating elements 24, and temperature control elements25 disposed on a first circuit board 21 a and a second circuit board 21b. The first circuit board 21 a is supported by metallic pins 27 a(hermetic terminals) serving as external terminals which are insulatedfrom, and pass through, a metallic base 26. The second circuit board 21b is supported by metallic pins 27 b implanted on the first circuitboard 21 a. Both the first circuit board 21 and the second circuit board21 b are composed of glass epoxy material.

The crystal resonator 22 comprises for example, an AT cut or SC cutcrystal piece sealed off inside a metallic case 29, shown in FIG. 6B,with a pair of lead wires 28 leading out. The thermostat 23 is formedwith a metallic cylinder 30 having a heating wire 31 wound therearound,and accommodates the crystal resonator 22 as also shown in FIG. 6A.Moreover, the principal plane of the metallic cylinder 30 is placed soas to face one principal plane of the second circuit board 21 b, andboth of these are thermally joined by a thermo-conductive resin 32.Furthermore, a pair of lead wires 28 of the crystal resonator 22 arebent and connected to the second circuit board 21 b.

The oscillating elements 24 constitute an oscillation circuit togetherwith the crystal resonator 22, and are disposed on the other principalplane of the second circuit board 21 b. The temperature control elements25 include at least a thermistor 25 a as a temperature sensitiveelement, and together with power transistors, construct a temperaturecontrol circuit that controls the temperature of the thermostat 23. Themembers apart from the thermistor 25 a are disposed on the peripheraledge of the first circuit board 21 a. In this temperature controlcircuit the temperature of the thermostat 23 is detected for example byjoining the thermistor 25 a to the thermostat 23. Then, based on thisdetected temperature, the power to be supplied to the heating coil 31 iscontrolled to maintain the temperature inside the thermostat 23constant. A metallic cover 33 covers these members.

According to such a crystal oscillator, the operating temperature of thecrystal resonator 22 can be controlled to be constant by the thermostat23, so that frequency fluctuations of the oscillation frequency due totemperature variation can be prevented. In other words, fluctuations inthe oscillating frequency based on the frequency temperaturecharacteristics of the crystal resonator 22 can be prevented. Moreover,since the second circuit board 21 b mounted with the oscillatingelements 24 is disposed on the thermostat 23, frequency fluctuations dueto the temperature characteristics of the circuit elements themselvescan be prevented.

However, as shown in FIG. 6B, since the crystal oscillator of the aboveconstruction uses the crystal resonator 22 in which a crystal piece isaccommodated in the metallic case 29 that has lead wires 28 leading outexternally, there is an increase in the size of the crystal oscillatoritself. Moreover, since the thermostat 23 with the heating coil 31 woundtherearound is used, the crystal oscillator itself becomes moreexpensive and its structure becomes more complex. There is also anoscillator in which the metallic container 29 of the crystal resonator22 has the heating coil 31 directly wound therearound. However, even inthis case, an operation for winding the heating coil 31 on thethermostat 23 is required, and hence in either case there is a problemof increased complexity of the structure.

Moreover, these crystal oscillators are employed for use in a basestation, as having a frequency stability of 0.05 ppm or less asdescribed earlier. However, since for example, GMS purpose requirescomparatively moderate frequency stability of 0.1 to 0.2 ppm or less,there have been instances of over specification. In light of this,application of a temperature compensated crystal oscillator for surfacemounting may be considered. However, in this case frequency stabilitybecomes approximately 1 ppm, and hence there is a problem in that it cannot satisfy predetermined standards.

An object of the present invention is to provide a constant temperaturetype crystal oscillator in which miniaturization is advanced, and thestructure is simplified.

SUMMARY OF THE INVENTION

The present invention is one where, in a lead wire led-out type crystaloscillator of constant temperature type for high stability, comprising:a heat supply body that supplies heat to a crystal resonator from whicha plurality of lead wires are led out, to maintain the temperatureconstant; an oscillating element that constitutes an oscillating circuittogether with the crystal resonator; a temperature control element thatconstitutes a temperature control circuit for controlling thetemperature of the crystal resonator; and a circuit board for mountingthe heat supply body, the oscillating element, and the temperaturecontrol element, and through which lead wires of the crystal resonatorare passed through for mounting, the heat supply body comprises: a heatconducting plate which has through-holes for the lead wires and ismounted on the circuit board, and which faces, and is directly thermallyjoined to, the crystal resonator; and a chip resistor for heating whichis mounted on the circuit board adjacent to the heat conducting plate,and is thermally joined to the heat conducting plate.

According to such a construction, the heat conducting plate is heated bythe chip resistor provided on the circuit board upon which theoscillating element and the temperature control element are mounted, andthe crystal resonator faces these and is directly thermally joined toboth items. Therefore a thermostat becomes unnecessary and only a singlecircuit board is required. As a result, the structure can be simplified,and in particular the height dimension of the oscillator itself can bereduced.

In the present invention, the heat conducting plate has firstconcavities on one pair of opposite end sides, and the chip resistorsthat have been thermally joined to the heat conducting plate aredisposed in the first concavities. As a result, the chip resistors aredisposed in geometrically stable symmetric positions, and the heatconducting plate can be heated uniformly.

Moreover, in the present invention there are second concavities in another pair of opposite end sides of the heat conducting plate, and powertransistors that have been thermally joined to the heat conducting plateare disposed in the second concavities. As a result, the heating bodies(chip resistors and power transistors) are disposed above, below, left,and right of the heat conducting plate, and the heat conducting platecan be heated even more uniformly. Moreover, by using the heat of thepower transistors, power consumption of the chip resistors can bereduced.

Furthermore, in the present invention, an aperture part is formed in thecenter area of the heat conducting plate, and a highlytemperature-dependent, highly heat sensitive element, among theoscillating element and the temperature control element, is disposedinside said aperture part so that it is thermally joined to the heatconducting plate. As a result, the temperature dependency of the highlyheat sensitive element can be resolved, and stable characteristics canbe obtained.

Moreover, in the present invention, the heat conducting plate isthermally joined to one principal plane of the circuit board, and theoscillating element is disposed on the other principal plane of thecircuit board, which faces the heat conducting plate. As a result,temperature characteristics of the oscillating element can be madeconstant, and oscillating frequency can be made more stable.

Furthermore, in the present invention, the thermal joining is carriedout by thermo-conductive resin. As a result, for example adhesionbetween the crystal resonator and the heat conducting plate can beimproved, and efficient heat conduction can be achieved.

In the present invention, a cut out is provided which passes through thecircuit board, and is peripheral to the heat conducting plate. As aresult, the heat conducting plate and the circuit board at the peripherythereof are thermally separated, and heat dissipation is prevented.

Moreover, the present invention is a constant temperature type crystaloscillator which uses a surface mounting crystal resonator, in which asurface mounting crystal resonator is mounted on the circuit boardtogether with an oscillating element and a temperature control element,and the construction is such that the crystal resonator is arranged on aceramic substrate, and at least a chip resistor for heat generation, anda highly temperature-dependent highly heat sensitive element arearranged on the ceramic substrate.

According to such a construction, the crystal resonator is made forsurface mounting, and the chip resistor for heating is disposed on theceramic substrate. Therefore, a constant temperature type crystaloscillator in which miniaturization is expedited and with a simplifiedstructure can be obtained. Moreover, since a highly heat sensitiveelement is arranged on the ceramic substrate, if this is a temperaturesensitive element for example, heating temperature can be directlydetected. Furthermore, if this as an oscillating element, itstemperature dependency can be resolved.

The crystal resonator of the crystal oscillator of the present inventionis arranged on one principal plane of the ceramic substrate, and thechip resistor and the temperature sensitive element are arranged on theother principal plane of the ceramic substrate. As a result, the chipresistor can be disposed facing the crystal resonator, and the heatefficiency can be improved. Also, the chip resistor is disposed adjacentto the temperature sensitive element, so that the heat generationtemperature can be directly detected.

In the crystal oscillator of the present invention, the crystalresonator is arranged on one principal plane of the ceramic substrate,and the chip resistor and the temperature sensitive element are arrangedon the other principal plane of the ceramic substrate, and the otherprincipal plane of the ceramic substrate is positioned facing oneprincipal plane of the circuit board, and thermo-conductive resin isprovided between the chip resistors and the circuit board, therebyadhering them. As a result, heat from the chip resistor can beefficiently transmitted to the circuit board, by the thermo-conductiveresin.

In the crystal oscillator of the present invention, an oscillatingelement that constitutes an oscillating circuit is arranged on the otherprincipal plane of the circuit board, which faces the ceramic substrate.As a result, heat is transmitted to the oscillating element to make thetemperature uniform. Therefore, fluctuations in the oscillating elementcharacteristics due to the temperature characteristics can be prevented.

In the present invention, the highly heat sensitive element is either atemperature sensitive element or a voltage-variable capacitive element.As a result, heat generation temperature of the chip resistor can bedirectly detected. Moreover, fluctuations in capacity due to temperaturecan be prevented, and a voltage controlled oscillator of stableoscillating frequency with respect to control voltage can be achieved.

In the crystal oscillator of the present invention, the circuit board isretained on the another circuit board for surface mounting by metallicpins. As a result, a constant temperature type crystal oscillator forsurface mounting can be obtained, and a further miniaturization isexpedited.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for explaining one embodiment of a highly stableoscillator of lead wire led-out type of the present invention, whereinFIG. 1A is a vertical sectional view thereof, and FIG. 1B is a plan viewof the main points.

FIG. 2 is a diagram for explaining a conventional highly stableoscillator of lead wire led-out type, wherein FIG. 2A is a partialvertical sectional view thereof, and FIG. 2B is a perspective view of acontainer (hat shape) accommodating a crystal oscillator.

FIG. 3 is a diagram for explaining one embodiment of a surface mountedcrystal oscillator of the present invention, wherein FIG. 3A is avertical sectional view of a constant temperature type surface mountedcrystal oscillator, and FIG. 3B is a plan view of a ceramic substrate.

FIG. 4 is a vertical sectional view for explaining another embodiment ofa constant temperature type surface mounted crystal oscillator of thepresent invention.

FIG. 5 is a vertical sectional view for explaining still anotherembodiment of a constant temperature type surface mounted crystaloscillator of the present invention.

FIG. 6 is a diagram for explaining a conventional surface mountedcrystal oscillator, wherein FIG. 6A is a vertical sectional view of aconstant temperature type crystal oscillator, and FIG. 6B is a schematicdiagram showing a crystal oscillator inserted into a thermostat.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment

Lead Wire Led-out Type Crystal Oscillator

FIG. 1 is a diagram for explaining one embodiment of a highly stableoscillator of lead wire led-out type of the present invention, whereinFIG. 1A is a partial vertical sectional view thereof, and FIG. 1B is aplan view of the main points.

The highly stable oscillator of the present invention comprises aconstant temperature type crystal oscillator in which the operatingtemperature of a crystal resonator is constant. Here, as shown in FIG.1A, this highly stable oscillator is constructed with an oscillatingelement 8 including a crystal resonator 7 (a crystal piece 7 a), andtemperature control elements 5, mounted on a single circuit board 1, anda heat supply body 11 attached thereto. The heat supply body 11comprises a heat conducting plate 12, and chip resistors 13 a and 13 bfor heating. Here a power transistor of the temperature control element5 is also used for heating.

The heat conducting plate 12 comprises an aluminum plate of for examplea square shape in plan view, and as shown in FIG. 1B, has a first pairof concavities 14 a on opposite end sides, a second pair of concavities14 b on opposite end sides orthogonal thereto, and an aperture part 15in its center area. The opposite end sides are positioned on concentriccircles having the center area as their center. Through-holes 16 throughwhich lead wires 9 of the crystal resonator 7 pass, are provided on theperipheral edge of the aperture part 15. Moreover, the four corners ofthe heat conducting plate 12 are fastened to the circuit board 1 withscrews. In the present embodiment, a thermo-conductive resin 12 b iscoated between the circuit board 1 and the heat conducting plate 12, tothermally join them. Furthermore, hook-shaped cut outs 17 that passcompletely through the circuit board 1, are provided opposite the fourcorners of the heat conducting plate 12.

The chip resistors 13 a and 13 b are provided as two, serving as heaterresistors using joule heat, and are respectively disposed in the firstpair of concavities 14 a of the heat conducting plate 12 mounted on thecircuit board 1. Also, power transistors 8 c and 8 d used for heating,are respectively disposed in the second concavities 14 b on the heatconducting plate 12. All of the terminals thereof are disposed adjacentto the periphery of the heat conducting plate 12 by means of soldering.A thermo-conductive resin is coated so as to cover the chip resistors 13a and 13 b, and the power transistors 8 c and 8 d. In this case, thethermo-conductive resin is also coated on the heat conducting plate 12,so the chip resistors 13 a and 13 b, and the power transistors 8 c and 8d are thermally joined to the heat conducting plate 12.

The crystal resonator comprises a crystal piece 7 a sealed off inside aTO8 type a crystal resonator 7 covered by a metallic container havingfive lead wires 9 leading out therefrom. Each lead wire 9 of the crystalresonator 7 passes through the through-holes in the heat conductingplate 12 and the circuit board 1, and is secured by soldering. In thiscase, the dimensions of the through-holes 16 in the heat conductingplate 12 are to be made greater than those of the through-holes in thecircuit board 1, so that the lead wires 9 and the heat conducting plate12 are electrically insulated. Moreover, the bottom of the crystalresonator 7 and the heat conducting plate 12 are facing opposed to eachother, and are directly thermally joined by a thermo-conductive resincoating therebetween, and are mounted on one principal plane of thecircuit board 1.

Among the oscillating elements 8 and the temperature control elements 5,a voltage-variable capacitive element 8 a and a thermistor 5 a, whichare highly heat sensitive elements, are disposed as shown in FIG. 1B inthe aperture part 15 provided in the central area of the heat conductingplate 12, and are thermally joined to the heat conducting plate 12 by athermo-conductive resin. Other oscillating elements 8 other than thehighly heat sensitive elements (8 a, 5 a) are disposed on the otherprincipal plane of the circuit board 1 opposed on the other side to theheat conducting plate 12, and the temperature control elements 5 arearranged and mounted on the peripheral edges of both principal planes ofthe circuit board 1.

According to such construction, the heat conducting plate 12 can beheated by the chip resistors 13 a and 13 b provided on the circuit board1, upon which the oscillating elements 8 and the temperature controlelements 5 are mounted. Furthermore, since the bottom of the metalliccontainer that accommodates the crystal resonator 7 is directlythermally joined to the opposing heat conducting plate 12, a thermostatis unnecessary, and the circuit board 1 can be constructed from a singlesubstrate. Therefore the construction can be made simple, and overall,in particular the height dimension of the crystal oscillator, can bemade small.

Moreover, the chip resistors 13 a and 13 b that have been thermallyjoined in the first concavities 14 a provided on the opposite end sidesof the heat conducting plate 12, are disposed on the heat conductingplate 12. Therefore, the chip resistors 13 a and 13 b are ingeometrically stable symmetric positions, and the heat conducting plate12 can be uniformly heated. Furthermore, the power transistors 8 c and 8d that have been thermally joined to the heat conducting plate 12, aredisposed in the second concavities 14 b provided on the opposite endsides orthogonal to the first concavities 14 a of the heat conductingplate 12. Therefore, the heating bodies (the chip resistors 13 a and 13b, and the power transistors 8 c and 8 d) are disposed above, below,left, and right of the heat conducting plate 12, and hence the heatconducting plate 12 can be even more uniformly heated. Moreover, byusing the heat of the power transistors 8 c and 8 d, electrical powerconsumption of the chip resistors 13 a and 13 b can be reduced.

Also, the aperture part 15 is provided in the center area of the heatconducting plate 12, and of the oscillating elements 8 and thetemperature control elements 5, the voltage-variable capacitive element8 a and the thermistor 5 a, which are highly temperature-dependenthighly heat sensitive elements, are thermally joined to the heatconducting plate 12 and disposed in the aperture part 15. As a result,the temperature dependency of the highly heat sensitive elements can beresolved, and stable characteristics can be obtained. Furthermore, theheat conducting plate 12 is thermally joined to one principal plane ofthe circuit board 1, and the oscillating elements 8 are disposed on theother principal plane of the circuit board 1, which is on the oppositeside. Therefore, the temperature characteristics of the oscillatingelements 8 can be made constant, and the oscillating frequency can befurther stabilized.

Moreover, since thermal joining of the crystal resonator 7 and the heatconducting plate 12 is achieved by having thermo-conductive resin inbetween them for example, they have good adhesion, and heat conductionis made more efficient. Furthermore, since the cut outs 17 are providedin the parts of the circuit board 1 positioned on the peripheral edge ofthe heat conducting plate 12, the heat conducting plate 12 and the partsof the circuit board 1 positioned on the peripheral edge thereof arethermally separated, thus preventing heat dissipation.

In the above embodiment, the crystal resonator 7 can be applied to a TO8type having five lead wires leading out. Moreover, the chip resistors 13a and 13 b and the power transistors 8 c and 8 d are respectively two innumber. However the number may be increased or reduced as necessary.Also, a single chip resistor 13 may be used.

Furthermore, the aperture part 15 provided in the center area of theheat conducting plate 12 may be substituted by the pair of concavities14 a and 14 b provided on opposite ends of the heat conducting plate 12.Alternatively, these concavities and the aperture part may be omitted,and a chip resistor 14 or the like may be simply provided on theperiphery edge of the heat conducting plate 12 having a square shape inplan view. Moreover, here for example the thermo-conductive resin isused for thermally joining the heat conducting plate 12 and the crystalresonator 7 a. However instead, a molten resin may be coated and cured,or a pre-cured sheet may be used. Moreover, since thermal joining isdependent on the degree of adhesion of both parts, the thermo-conductiveresin may not be deemed necessary.

Surface Mounted Crystal Oscillator

FIG. 3 is a diagram for explaining one embodiment of a surface mountedcrystal oscillator of the present invention, wherein FIG. 3A is avertical sectional view of a constant temperature type crystaloscillator, and FIG. 3B is a plan view of a ceramic substrate (seen fromthe back side of the crystal oscillator) used for the crystal oscillatorof the present invention.

First of all, as shown in FIG. 3A, the surface mounted crystaloscillator of the present invention is provided with a first circuitboard 21 a, and a second circuit board 21 b formed from glass epoxy. Thefirst circuit board 21 a comprises a multilayer substrate, and isprovided with a circuit pattern in its multilayer plane, and hasmounting terminals 36 for surface mounting, on its outer surface. Athermo-conductive ceramic substrate 34 that is held by metallic pins 27b, is provided on one principal plane of the second circuit board 21 b.Moreover, oscillating elements 24 that constitute an oscillator circuitare arranged in the central area of the other principal plane, andtemperature control elements 25 that constitute a temperature controlcircuit are arranged on the peripheral part thereof.

A crystal resonator 22 for surface mounting is arranged on one principalplane of the ceramic substrate 34. This surface mounted resonator 22 hasa crystal piece sealed off inside a ceramic container, and has amounting terminal for example on the bottom face of a rectangular part.Two chip resistors 35 a and 35 b for heat generation are arrangedopposite to the crystal resonator 22, in the central area of the otherprincipal plane opposed to the second circuit board 21 b.

Moreover, a thermistor 25 a is arranged between the chip resistors 35 aand 35 b as a temperature sensitive element, among the temperaturecontrol elements. Respective mounting terminals are integrally securedto these crystal resonator 22, chip resistors 35 a and 35 b, andthermistor 25 a by reflowing, such as with solder.

Moreover, as shown in FIG. 3A, a thermo-conductive resin 32 is disposedbetween the surfaces of the chip resistors 35 a and 35 b, and the secondcircuit board 21 b, and the ceramic substrate 34 is arranged on oneprincipal plane side of the second circuit board 21 b using the metallicpins 27 b. A clip part provided on the aperture edge of a metallic cover33 is inserted into an opening provided in the periphery of the firstcircuit board 21 a, and engaged, thus joining both parts. In this way,the second circuit board 21 a is accommodated.

In such a surface mounted crystal oscillator of the present invention,electricity is supplied through the power transistors of the temperaturecontrol circuit to the heat generation chip resistors 35 a and 35 b. Asa result, the joule heat of the chip resistors 35 a and 35 b isconducted to the ceramic substrate 34 thus heating it. The crystalresonator 22 secured to the ceramic substrate 34 is similarly heated viathe mounting terminal used for surface mounting. Moreover, thetemperature of the ceramic substrate 34 arranged on the crystalresonator 22 is directly detected by the thermistor 25 a to controlelectricity supply.

The heat of the chip resistors 35 a and 35 b is efficiently transmittedto the second circuit board 21 b by the thermo-conductive resin 32adhering between the one principal plane of the second circuit board 21b and the chip resistors 35 a and 35 b. Since the oscillating elements25 are arranged in the part opposed to the chip resistors 35 a and 35 bon the other principal plane of the second circuit board 21 b, theirtemperature dependency can be resolved.

According to such a construction, the crystal 25 oscillator can be madesmaller than a conventional crystal resonator with lead wires leadingout, because the crystal resonator 22 is for surface mounting. Since theheat source of the crystal resonator 22 is the chip resistors 35 a and35 b and the ceramic substrate 34, the structure of the crystaloscillator can be made simpler, and the crystal oscillator can bemanufactured inexpensively without the operation of winding the heatingwire, compared to a conventional crystal oscillator having the heatingwire wound around the thermostat.

Moreover, in the present invention, since the first circuit board 21 ais for surface mounting with mounting terminals 36, a conventionalmetallic base is rendered unnecessary, further advancing miniaturization(shortening).

In the above embodiments of the present invention, the crystaloscillator is for surface mounting, however it may be constructed asshown in FIG. 4. That is, in the embodiment shown in FIG. 4, a circuitboard 21 may be directly held by metallic pins 27 a that arehermetically mounted to a metallic base 26, similarly to theconventional example. In this embodiment the second circuit board 21 bshown in FIG. 3A becomes unnecessary.

Furthermore, as shown in FIG. 5, the second circuit board 21 b may besealed off inside a metallic cover 33, with a metallic base 26 forresistance welding for example. In this case, since each of theoscillating elements 24 and the temperature control elements 25 issealed off, they are isolated from the external atmosphere, and agedeterioration characteristics can be improved.

Moreover, in the embodiments of the present invention described above,only the thermistor 25 a is disposed on the other principal plane of theceramic substrate 14 as shown in FIG. 3A. However, for example a highlyheat sensitive element such as a voltage capacitive element having hightemperature dependency may be disposed on the ceramic substrate tofurther prevent frequency fluctuations due to the temperature.Furthermore, only the chip resistors 35 a and 35 b for heating aredisposed on one principal plane of the ceramic substrate 34 as shown inFIG. 3A. However, for example the power transistors of the temperaturecontrol circuit may be disposed for heat supply.

Furthermore, as shown in FIG. 3A, the crystal resonator 22 is providedon one principal plane of the ceramic substrate 34, and the chipresistors 35 a and 35 b and the thermistor 25 a are provided on theother principal plane of the substrate 34. However, since the ceramicsubstrate 34 has excellent heat conductivity and its macroscopic heatdistribution is uniform, arranging these members on the same principalplane would result in a similar effect.

1. A constant temperature type crystal oscillator comprising: a heatsupply body that supplies heat to a crystal resonator from which aplurality of lead wires are led out, to maintain the temperatureconstant; an oscillating element that constitutes an oscillating circuittogether with said crystal resonator; a temperature control element thatconstitutes a temperature control circuit for controlling thetemperature of said crystal resonator; and a circuit board for mountingsaid heat supply body, said oscillating element, and said temperaturecontrol element, and through which lead wires of said crystal resonatorare passed through the mounting, wherein said heat supply bodycomprises: a heat conducting plate which has through holes for said leadwires and is mounted on said circuit board, and which faces, and isdirectly thermally joined to, said crystal resonator; and a chipresistor for heating which is mounted on said circuit board adjacent tosaid heat conducting plate, and is thermally joined to said heatconducting plate, wherein said heat conducting plate has firstconcavities on a first pair of opposite end sides, and said chipresistors that have been thermally joined to said heat conducting plateare disposed inside said first concavities, wherein said concavitiesextend through the entire heat conducting plate in the direction of saidthrough holes.
 2. A constant temperature type crystal oscillatoraccording to claim 1, which has second concavities in a second pair ofopposite end sides of said heat conducting plate which are orthogonal tosaid first pair of opposite end sides, and power transistors that havebeen thermally joined to said heat conducting plate are disposed in saidsecond concavities.
 3. A constant temperature type crystal oscillatorcomprising: a heat supply body that supplies heat to a crystal resonatorfrom which a plurality of lead wires are led out, to maintain thetemperature constant; an oscillating element that constitutes anoscillating circuit together with said crystal resonator; a temperaturecontrol element that constitutes a temperature control circuit forcontrolling the temperature of said crystal resonator; and a circuitboard for mounting said heat supply body, said oscillating element, andsaid temperature control element, and through which lead wires of saidcrystal resonator are passed through the mounting, wherein said heatsupply body comprises: a heat conducting plate which has through holesfor said lead wires and is mounted on said circuit board, and whichfaces, and is directly thermally joined to, said crystal resonator; anda chip resistor for heating which is mounted on said circuit boardadjacent to said heat conducting plate, and is thermally joined to saidheat conducting plate; and an aperture part in a center area of saidheat conducting plate, and a temperature-dependent, heat sensitiveelement, among said oscillating element and said temperature controlelement, is disposed inside said aperture part so that it is thermallyjoined to said heat conducting plate, wherein said aperture extendsthrough the entire heat conducting plate in the direction of saidthrough holes.
 4. A constant temperature type crystal oscillatoraccording to claim 1, wherein said heat conducting plate is thermallyjoined to one principal plane of said circuit board, and saidoscillating element is disposed on the other principal plane of saidcircuit board, which faces said heat conducting plate.
 5. A constanttemperature type crystal oscillator according to claim 1, wherein saidthermal joining is through the medium of thermo-conductive resin.
 6. Aconstant temperature type crystal oscillator according to claim 1,wherein a cut out, which passes through said circuit board, is providedat a position corresponding to the periphery of said heat conductingplate.
 7. A constant temperature type crystal oscillator which uses asurface mounting crystal resonator, in which a surface mounting crystalresonator is mounted on a circuit board together with an oscillatingelement and a temperature control element, wherein said crystalresonator is arranged on a ceramic substrate, and at least a chipresistor for heat generation, and a temperature-dependent heat sensitiveelement are arranged on said ceramic substrate, wherein said crystalresonator is arranged on a first principal plane of said ceramicsubstrate, and said chip resistor and said heat sensitive element arearranged on a second principal plane of said ceramic substrate, and thesecond principal plane of said ceramic substrate is positioned facingone principal plane of said circuit board, and thermo-conductive resinis provided between said chip resistor and said circuit board, so thatsaid chip resistor and said circuit board are adhered.
 8. A constanttemperature type crystal oscillator according to claim 7, wherein anoscillating element that constitutes an oscillating circuit is arrangedon the other principal plane of said circuit board, which faces saidceramic substrate.
 9. A constant temperature type crystal oscillatoraccording to claim 7, wherein said heat sensitive element is either atemperature sensitive element or a voltage-variable capacitive element.10. A constant temperature type crystal oscillator according to claim 7,wherein said circuit board is retained on another circuit board forsurface mounting by metallic pins.